1. Field of the Invention
The present invention relates to a printing apparatus capable of printing on both faces of roll paper.
2. Description of the Related Art
For example, both side printing mechanisms capable of printing simultaneously on both faces of thermal recording paper are known. In the both side printing mechanisms, a first printing section having a first thermal head and a first platen roller across a paper feed path, and a second printing section having a second thermal head and a second platen roller across the paper feed path are arranged symmetrically.
In the both side printing mechanisms, the first thermal head executes printing on a front face of thermal recording paper passing through the paper feed path, and the second thermal head executes printing on a rear face of the thermal recording paper, so that a printing process can be executed on both faces of the thermal recording paper (for example, see Jpn. Pat. Appln. KOKAI Publication No. 11-286147).
In such a kind of printing apparatuses, a first printing section is arranged on a downstream side of a paper feed direction, and a second printing section is arranged on an upstream side of the paper feed direction in a paper feed path. The first and second printing sections execute printing simultaneously on both faces of paper.
The first printing section has a first thermal head as a printing head, and a first platen roller which is arranged to be opposed to the first thermal head via the paper feed path and feeds paper. The second printing head has a second thermal head as a printing head, and a second platen roller which is arranged to be opposed to the second thermal head via the paper feed path and transports the paper. The first and second thermal heads, and the first and second platen rollers are positioned on opposite sides of the paper feed path, respectively, so that the printing can be executed simultaneously on both faces of paper (for example, see U.S. Pat. No. 6,784,906).
It is considered that the similar constitution to that of the both side printing mechanisms is applied to thermal printers having an upper frame capable of being opened/closed with respect to a main body. In such thermal printers, for example, the main body includes only a first platen roller and a second thermal head. The upper frame is disposed with a first thermal head and a second platen roller, for example. When the thermal heads and the platen rollers are arranged in separated members, it is necessary to locate the thermal heads and the platen rollers. For this reason, the second thermal head of the cover body is located on the second platen roller of the main body, and the first platen roller of the cover body is located on the first thermal head of the main body by using an operation for bringing an opened state of the cover body into a closed state.
In the thermal printers having the above constitution, the thermal heads and the corresponding platen rollers are separately arranged in the upper frame and the main body, respectively. Thus, when they are arranged in desired positions, they should be located with high accuracy. For this reason, the management of the position accuracy takes efforts and is expensive, and the entire thermal printer needs high production cost.
Paper is of a roll type, and is mounted into the apparatus main body and is pulled out to be set across the first and second printing sections for use. When the paper is used up, the paper should be replaced with new one, in which case an open/close member on the upper face side of the apparatus main body is opened so that the paper is replaced with new one.
Since the open/close member is, however, opened manually by an operator totally, this operation takes efforts.
The printing is not always executed on both faces of thermal recording paper, and occasionally the printing is executed on only one face. However, since the thermal heads always touch thermal recording paper, the thermal heads abrade away due to friction with thermal recording paper, and thus thermal recording paper should be frequently replaced. Since useless load is applied to the mechanism of a driving system, malfunction easily occurs.
Since the thermal heads are expensive parts in parts composing a printer, both side printing thermal printers become more expensive than one side printing thermal printers. For this reason, when users, who need only the one side printing at the present moment but possibly needs the both side printing later, purchase the both side printing thermal printers at first, the initial introduction cost becomes high. On the other hand, when the one side printing thermal printer is purchased at first and the both side printing thermal printer is purchased at the time of the both side printing, it is uneconomical because the transport mechanism and the like can be shared.